Installing architectural moulding inside a room or to a building exterior is an increasing trend in building construction and renovation. When tastefully designed, it adds a degree of elegant decoration that enhances the esthetics of the business or residence, and potentially increases property values. Crown mouldings are typically fashioned as an elongated strip of decorative material installed at an angle at the juncture between walls and ceilings, ledges or overhanging roofing but can find other applications including capping walls, pilasters, cabinets, cornice assemblies or door and window hoods. Crown mouldings can be manufactured in a variety of materials. Historically crown mouldings were milled from wood or cast in plaster. Today crown mouldings are available in plaster, solid wood, finger joint wood construction, medium density fibreboard (MDF), polyurethane, PVC, fiberglass, polystyrene and plaster-coated foam mouldings.
Conventional lineal crown moulding is an elongated piece of material having a front surface with a decorative profile and a generally flat back surface. Crown mouldings that are cast or extruded have a front surface with a decorative profile, but the back surface is more likely to be non-planar to reduce the amount of material used to form the moulding.
Regardless of the material of construction, the entire front surface is decorative and serves no functional purpose. The crown moulding is typically applied against a ceiling and a wall at an angle. Crown moulding typically comes in three different spring angles: 38°, 45°, and 52°. The spring angle is the “tilt” at which the crown moulding sits on the wall. The different spring angles are a way to show off the moulding detail better at different wall heights. For example, on a lower ceiling you want the crown moulding to tilt up towards the eye for better viewing. In the same way crown moulding set into a high ceiling looks best when ifs tilted down.
The spring angle or tilt is accomplished by providing a top chamfer portion on the back surface which is placed against the ceiling (“ceiling seat”) and a bottom chamfer portion on the back that is placed against the wall (“wall seat”). With a 38° spring angle, the moulding is tilted at an angle of 38° relative to the wall and at an angle of 52° relative to the ceiling with the wall seat flat against the wall and the ceiling seat flat against the ceiling. This provides a crown moulding mounted further down the wall.
With a 52° spring angle, the moulding is tilted at an angle of 52° relative to the wall and at an angle of 38° relative to the ceiling with the wall seat flat against the wall and the ceiling seat flat against the ceiling. This provides a crown moulding mounted further along the ceiling.
With a 45° spring angle, the moulding is tilted at an angle of 45° relative to the wall and at an angle of 45° relative to the ceiling with the wall seat flat against the wall and the ceiling seat flat against the ceiling. This provides a crown moulding mounted equi-distant down the wall and along the ceiling.
Because crown moulding is mounted at an angle between the wall and ceiling, as opposed to flat against either the wall or the ceiling, it is difficult to cut. Further installation, in a room or other space, typically, can be time consuming in order to have the mouldings fit together in or around corners or other objects as seamlessly as possible. The possibility of errors is high and there is a significant amount of waste material. When cutting crown moulding to fit an inside or outside corner, to form the angles required to install crown molding with a mitred corner, the moulding must be cut in two directions at once; first it must be beveled and second it must be mitered. There are two different methods commonly used: vertical nested or flat.
The vertical nested method can be undertaken with either a mitre saw or compound mitre saw and is applicable to crown moulding regardless of the materials of construction or design of the moulding, provided, the saw has sufficient vertical stroke to accommodate the crown vertical nested on the saw table. Large sizes of crown mouldings, where the height of the moulding precludes vertical nesting, must be cut flat. Typically wood and MDF crown moulding are cut and installed using either a mitre saw or compound mitre saw. With moulding made from materials that are easier to cut than solid hardwoods or MDF, a mitre box and hand saw can be used. With a mitre saw or hand saw and a mitre box, the blade remains perpendicular to the saw table or base of the mitre box, but the blade is positioned to cut at an angle relative to the fence of the mitre saw or back wall of the mitre box.
Cutting crown moulding flat requires a compound mitre saw and crown moulding with a flat back surface. This is particularly true for large sizes where the vertical stroke of the saw is not sufficient to permit cutting using the vertical nesting method. With a compound mitre saw not only can the blade and table be rotated horizontally relative to the fence, the vertical angle of the blade can also be adjusted.
When cutting crown moulding using the vertical nested method, the moulding is placed with the wall seat on the bottom of the back surface of the moulding resting squarely against the fence or back wall of the mitre box and with the ceiling seat on the top of the back surface of the moulding resting squarely on the base of the saw or mitre box. Placing the moulding on the saw at the same angle as it will be installed creates the right bevel. To cut the crown moulding to create the mitre to fit an inside mitred corner, for the left side of the corner, set the saw angled to the right to half the exact angle of the first corner, schematically illustrated as \. Whether cutting for an inside or outside corner, few rooms have a perfectly square corner. In order to quickly find the exact degree of the corner, use an angle finder is required.
Save the piece of moulding to the right of the saw—the piece to the left of the saw is scrap. For the right side of the corner, reset the saw angled to the left to half the exact angle of the first corner, schematically illustrated as /. Save the piece of moulding to the left of the saw—the piece to the right of the saw is scrap.
To cut the crown moulding to fit an outside mitred corner, for the left side of the corner, set the saw angled to the left to half the exact angle of the first corner, schematically illustrated as /. Save the piece of moulding to the right of the saw—the piece to the left of the saw is scrap. For the right side of the corner, reset the saw angled to the right to half the exact angle of the first corner, schematically illustrated as \. Save the piece of moulding to the left of the saw—the piece to the right of the saw is scrap. Holding the moulding in place consistently at the proper angle while cutting can be difficult and various jigs have been developed to try and make it easier. If the two mitre cuts are off slightly the two pieces of moulding will not form a perfect mitred corner.
A compound mitre saw makes it possible to make the bevel and mitre cuts at the same time with the flat back surface of the crown moulding lying flat on the saw table. The angles for crown mouldings are very precise and difficult to set exactly. Since the mouldings can shift slightly and very few rooms have perfectly square corners, typically all saw settings are first tested on scrap pieces. Charts have been developed providing appropriate mitre-bevel settings for mouldings with 52°/38°, 38°/52°, and 45°/45° ceiling to wall seat angles for a wide range of corner angles. For example:
52°/38° Crown Moulding45°/45° Crown MouldingAngle betweenMitreBevelMitreBevelwallsSettingSettingSettingSetting8633.4335.1937.1731.148732.9734.8636.6930.868832.5234.5336.2130.578932.0734.2035.7430.299031.6233.8635.2630.009131.1733.5334.7929.719230.7333.1934.3329.429330.3032.8533.8629.13
To cut the crown moulding to create the mitre to fit an inside mitred corner, using crown moulding with a spring angle of 52°/38°, for the left side of the corner, place the moulding with the back side flat against the table and the top edge of the moulding against the fence. Check the charts for a 90° corner (or other angle for the corner as measured) and set the mitre angle of the saw blade to the right, schematically illustrated as \, at 31.62° and the bevel angle at 33.86°. The piece to the left of the saw is the good piece the piece to the right of the cut is scrap. For the right side of the corner, place the moulding with the back side flat against the table and the bottom edge of the moulding against the fence. Re-set the mitre angle of the saw blade to the left, schematically illustrated as/at 31.62° and the bevel angle at 33.86°. The piece to the left of the saw is the good piece, the piece to the right of the cut is scrap. Trying to cut the moulding face down is problematic with a non-planar profile that has uneven thicknesses and may have a tendency to rock.
To cut the crown moulding to fit an outside mitred corner, for the left side of the corner, place the moulding with the back side flat against the table and the bottom edge of the moulding against the fence. Check the charts for a 90° corner and set the mitre angle of the saw to the left, schematically illustrated as/at 31.62° and the bevel angle at 33.86°. The piece to the right of the saw is the good piece the piece to the left of the cut is scrap. For the right side of the corner, place the moulding with the back side flat against the table and the top edge of the moulding against the fence. Re-set the mitre angle of the saw blade to the right, schematically illustrated as \ at 31.62° and the bevel angle at 33.86°. The piece to the right of the saw blade is the good piece the piece to the left of the cut is scrap.
For moulding with a different spring angle or for corners other than 90°, the mitre angles and bevel angles will be different.
From the foregoing it is evident that cutting and installing crown moulding takes considerable skill. In some cases a jig may be required. Further it is time consuming to set the saw, measure, cut a piece, re-set the saw, measure and cut a second piece to finish one corner. In addition there is a significant amount of waste as only the piece on one side of the saw blade after each cut can be used and the piece on the other side of the saw blade is scrap. Also the frequency of an error in setting the saw and cutting the piece for one side of the corner is relatively high resulting in additional waste of time and materials.
To avoid having to mitre-cut the crown moulding to fit precisely into inside corners or around outside corners, pre-mitred corners have been manufactured to fit a 90° inside corner or outside corner. The pre-mitred corners are made from short sections of crown moulding, usually about six to eight inches and are made with the most common profiles. By installing the pre-mitred corners in the room the installer then only has to cut the crown moulding to the correct length to butt up against the ends of the pre-mitred corners. It is important that the profile on the pre-mitred corners match exactly the profile of the lineal crown moulding. The Wood Moulding & Millwork Producers Association have standardized a number of different profiles and different sizes.
A difficulty in practical terms is that most rooms consist of inside corners, rather than outside corners. With pre-mitred corners two SKUs are required per profile and size of moulding, one for inside corners and a second for the outside corners. About 4 to 5 inside corners are sold for every outside corner. Therefore there is an extensive amount of additional shelf or bin space required for two SKUs and an extensive amount of waste of outside corners which eventually cannot be sold and are scraped. In addition the pre-mitred corners are commonly made for 90° inside corners or outside corners. But as noted above most rooms are not perfectly square with 90° corners. In situations where the corners are not 90° use of pre-mitred corners is precluded.
Another way to avoid having to cut mitred corners involves the use of corner boxes. Corner boxes have a decorative and functional purpose. One type of corner box to fit an inside corner has two flat pieces of material joined at their ends to form a right angle. The pieces are wider than the height of the crown moulding so when the top edge of the flat pieces rests against the ceiling, the end of the crown moulding butts against the flat piece. A decorative element depends from the bottom side of the flat pieces. The decorative element is typically formed of pieces of flat back crown moulding formed as an outside corner but do not have to match the profile of the crown moulding being installed. Alternatively the corner block can be made of one solid piece of material. The corner blocks for an outside corner are a notched square box larger than the height of the crown moulding so when the top edge of the box rests against the ceiling, the end of the crown moulding butts against the flat side of the box. A decorative element depends from the bottom of the box. The decorative element is typically formed of pieces of flat back crown moulding formed as outside corners but do not have to match the profile of the crown moulding being installed. Alternatively the corner block can be made of one solid piece of material. Use of the corner blocks eliminates the need to make mitred inside or outside corners when installing the crown moulding.
In an effort to make cutting the crown moulding easier numerous jigs to hold the crown moulding in position on the saw have been developed. See for example U.S. Pat. Nos. 7,360,476; 6,782,782; 6,422,117; 5,730,434; 4,907,482; and 4,875,399.
The invention described herein provides a solution to the difficulty in cutting and installing crown moulding and doing so in less time and with less waste than with products currently available.